5. I did not tell them the truth. => They
6. Did you give them the books that I bought? => Were
7. Did he send the letter for me? =>Was
8. Why didn’t they help him? => Why wasn’t
9. How did the police find the lost man? => How was
10. Who lent you that book? => By whom
5. I did not tell them the truth. => They weren't told the truth
6. Did you give them the books that I bought? => Were they given the books that I bought
7. Did he send the letter for me? =>Was the letter sent for me by him
8. Why didn’t they help him? => Why wasn’t he helped
9. How did the police find the lost man? => How was the lost man found by the police
10. Who lent you that book? => By whom were you lent that book